Carding machine fiber and air control method and means

ABSTRACT

A method and enabling means is provided for controlling to substantially improved advantage the troublesome air currents generated in carding machines at the surface of the lickerin roll beyond its tangency with the carding cylinder, and for additionally and comparably controlling the character of fiber going forward on any carding machine roll surface at which appreciable air currents are generated.

United States Patent 1191 ONeal et al.

[ June 12, 1973 CARDING MACHINE FIBER AND AIR CONTROL METHOD AND MEANS [76] Inventors: James Everett ONeal; Josef Karl Gunter; Colie Walton Gunter, all of c/o Gunter & Cooke, lnc., P. O. Box 339, Durham, NC.

22 Filed: Apr. 30, 1969 211 Appl. No.: 820,684

Related US. Application Data [63] Continuation of Ser. No. 629,842, Feb. 14, 1967, abandoned, which is a continuation-in-part of Ser. No. 535,126, March 17, 1966, abandoned.

52 us. (:1. 19 107 51 1111.01 D0lg 15/76 [58] Field of Search 19/107, 109

[56] References Cited 3 UNITED STATES PATENTS Landreth 19/83 Reiterer 19/105 Bryan, Jr. 19/107 X Primary Examiner-Dorsey Newton Attorney-Richards, Shefte & Pickney [57] ABSTRACT A method and enabling means is provided for controlling to substantially improved advantage the troublesome air currents generated in carding machines at the surface of the lickerin roll beyond its tangency with the carding cylinder, and for additionally and comparably controlling the character of fiber going forward on any carding machine roll surface at which appreciable air currents are generated.

10 Claims, 6 Drawing Figures PATENm, JUN] 21915 sum 2 0r 3 L n l k R 6 O .N maumw m 11 0 676 E T N 0 000 R m a m H1 in r mmm F 1 MP W .J W W k. H. mm |H 2 NM H lxll N.

PATENTED .mm 2 ms SHEET 3 OF 3 INVENTORS JAMES :vcnzrr OwgAL, J'OslF' KARL GUNTER e, BY CGLIE WALTON GUIIT'ER ATI'ORN Y5 CARDING MACHINE FIBER AND AIR CONTROL METHOD AND MEANS CROSS-REFERENCE TO RELATED APPLICATIONS This is a continuation of copending application Ser. No. 629,842, filed Feb. 14, 1967 now abandoned, which in turn a continuation-in-part of copending application Ser. No. 535,126, filed Mar. 17, 1966, now abandoned.

BACKGROUND OF THE INVENTION In cotton carding machines the fiber to be carded is conventionally delivered from a lap over a feed plate by the action of a feed roll which presents the leading edge or fringe of the lap to a lickerin roll that combs fiber therefrom and transfers it to the carding cylinder at which the lickerin runs tangent. The fiber must be thinned considerably from its lap form in transferring it to the cylinder, and for this reason the lickerin roll is 1 rotated at a relatively high speed which must have a proportionate correspondence with the cylinder speed and must be increased proportionately with increasing cylinder speed. Accordingly, while lickerin speeds of about 500 RPM. and less were common at the conventional cylinder or carding speeds heretofore in use, the recent trend toward high speed carding has resulted in required lickerin speeds in the order of 800-900 RPM. and more.

During operation both the carding cylinder and the lickerin generate surface air currents that cause a troublesome high pressure zone beyond the lickerin feeding tangency, from which undesirable fiber disturbance tends to result. At the conventional relatively slow carding speeds, it has proved possible to control these high pressure air currents tolerably by shrouding the cylinder and lickerin surfaces beyond their feeding tangency with arcuate cover plates that contained and directed the air currents in a reasonably controlled and relatively harmless manner.

As carding speeds are increased, however, there must be some relief of the high pressure zone above the lickerin in order to prevent inordinate fly formation and to control the air currents satisfactorily in the region of the feed roll. But when relief of this high pressure zone is attempted a difficult problem of waste control is encountered, because the lickerin does not transfer cleanly. or completely to the cylinder. That is, of the fiber carried at the surface of the lickerin after it passes the feed roll and feed plate, something in the order of percent will not transfer to the cylinder and will, consequently, be retainedat the lickerin surface during its rotating return to the feed roll. This retained percentage is largely'good fiber and should not be lost,- but it is readily subject to being lost or carried off to waste by relief of the high pressure zone above the lickerin. Additionally, some portion of the retained fiber on the lickerin as well as that transferred and going forward on the carding cylinder is short fiber that is undesirable for many purposes, and it would improve the carding result appreciably if this short fiber could be removed effectively.

SUMMARY OF THE INVENTION The present'invention solves the foregoing problem at the lickerin tp exceptional advantage by shrouding the lickerin surface concentrically and relatively closely for an initial extent beyond the feeding tangency with the cylinder, so as to direct the high pressure air currents initially for seating the untransferred fiber in the teeth of the lickerin, and then relieving'the high pressure zone in advance of the feed roll by withdrawing air from the lickerin roll surface reversely with respect to the traveling direction of its teeth (i.e., the direction of lickerin rotation). A related resulting advantage of this method of air release is that it serves additionally to withdraw and allow collection readily of the dust and short fiber fly that is always entrained by the lickerin air currents and that is normally exhausted to the atmosphere when these air currents reach the feed roll. Comparable means may also be arranged at the surface of the carding cylinder not only to control the air currents generated thereat but also to provide for removal of undesirable short fiber therefrom, as well as from the lickerin reach beyond transfer.

BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings show an embodiment of the invention arranged to operate in the foregoing manner. In these drawings:

FIG. 1 is a vertical section diagram indicating the operating disposition of a lickerin air control means according to the present invention;

FIG. 2 is a fragmentary plan detail of the concentric lickerin shroud plate employed, as it appears from the direction indicated at 2-2 in FIG. 1;

FIG. 3 is a plan of the superstructure spacers, as seen from above in the direction indicated at 3-3 in FIG.

FIG. 4 is a further fragmentary plan detail of the eccentric lickerin shroud plate, as seen from the 44 direction in FIG. 1;

FIG. 5 is an elevation, partly broken in length, of the suction hood superstructure as seen from the right in FIG. 1; and

FIG. 6 is a diagrammatic illustration of the manner in which an air control means may be provided at the carding cylinder as well as at the lickerin in accordance with the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The FIG. 1 illustration shows the lickerin roll at 10 arranged for rotation downwardly past the feed roll 12 and feed plate 14 and over suitable understructure 16 to eventual feeding tangency with the carding cylinder 18, at which both the cylinder 18 and lickerin 10 are rotating upwardly. 1

The high pressure air currents generated at the respective surfaces of the lickerin l0 and cylinder 18 beyond the feeding tangency are indicated generally by directional arrows at 10 and 18'. The portion of these air currents that follows the surface of the cylinder 18, as at 18', passes upwardly beneath a cylinder cover plate of the usual form as indicated at 20, so as to be controlled in this way until the action of the card flats (not shown) is about to commence on the fiber that the cylinder 18 carries and the high pressure air may, therefore, be released with a minimum of fiber disturbance.

However, the high pressure air current portion 10 that follows the lickerin surface is normally directed back to the feed roll 12 and must be contained specially there, either by some sort of feed roll cover member or by a riding roll or the like, in order to avoid troublesome air disturbance adjacent the lap delivery point. There has been considerable prior art activity dealing with alternative arrangements for redirecting the air currents to better advantage at the feed roll or for releasing them beforehand, but a fully satisfactory alternative has not been devised, and the necessity for improving conventional practice has become acute at current higher carding speeds.

The present invention deals with this problem, as previously noted, by causing the lickerin air currents '10 initially to influence untransferred fiber toward seating in the teeth of the lickerin l0, and then releasing these currents reversely before the feed roll 12 is reached. For this purpose, the lickerin cover structure is arranged to incorporate complementary concentric and eccentric arcuate cover plates 22 and 24.

The concentric cover plate 22 has arcuate positioning straps 26 attached beneath its end portions (compare FIGS. 1 and 2) for mounting in the usual manner on the end cover members (not shown) conventionally provided on the card frame at each end of the lickerin 10 adjacent the bearing stands that carry it. As thus mounted, the cover plate 22 is disposed concentrically and in relatively close shrouding relation over the lickerin l0, and its mounted disposition and arcuate extent are arranged so that it reaches arcuately from converging and abutting relation with the cylinder cover plate to an opposite edge portion that terminates appreciably short of the feed roll 12.

How far short of the feed roll 12 this opposite edge portion of the cover plate 22 is made to terminate is subject to some variation as a matter of choice. In general, the concentric reach of the cover plate 22 from abutment with the cylinder cover plate 20 must be great enough to allow sufficient overhead room for an effective reverse release of the air currents 10, while the reach must not be so great as to prevent effective air release short of the feed roll 12. Between these extreme limits, it appears that the greater the concentric reach of the cover plate 22 the less tendency there is for fiber to be wasted from the lickerin 10 with the air release. The concentric proportioning of the cover plate 22 that is indicated in FIG. 1 has been found to provide an advantageous balance of the foregoing considerations where minimum fiber waste is desired.

The complementary eccentric cover plate 24 is arranged to overlap the terminal or downstream edge portion of the concentric cover plate 22 from a pivotal mounting adjacent the feed roll 12 as indicated at 28 in FIG. 1. The pivotal mounting at 28 is effected between spacer members 30 (compare FIGS. 1 and 3) that are shaped arcuately and at the same width for assembly above the positioning straps 26 carrying the cover plate 22. The spacers 30 taper from an end portion of considerable height, that is formed to nest closely at the ends of the feed roll 12, to an opposite end portion of substantially reduced thickness, which extends toward the cylinder cover plate 20. Assembly of the spacers 30 above the positioning straps 26 is effected with suitable fastening screws as indicated at 32 in FIG. 1, and the bottom face of each spacer 30 is stepped to provide for sandwiching of the concentric cover plate 22 beneath the tapering spacer portions that extend thereover.

From its pivotal mounting at 28 adjacent the feed roll 12, the eccentric cover plate 24 extends between the spacers 30 to overlap the adjacent edge portion of the concentric cover plate 22, as previously mentioned. The extending edge portion of. the cover plate 24 is suitably formed for such overlapping with a turned edge configuration, as at 34, that doubles back in spaced relation and is extended endwise to'provide ear portions 36 (compare FIGS. 1 and 4) in which adjusting screws 38 may be fitted for setting the eccentricity of the cover plate 24. The spacers 30 have their adjacent side faces notched, as indicated best at 40in FIG. 3, to clear the cover plate ear portions 36 and allow the adjusting screws 38 to engage the positioning straps 26 for adjustment setting. By such adjusting arrangement the overlapping edge portions of the cover plates 22 and 24 may be spaced to form an air release slot of selected width, and coextensive in length with the lickerin 10, through which a reversely directed release of air may be directed in accordance with the present invention.

In order to induce the reversely directed air release a suction hood superstructure is provided as indicated generally in FIG. 1 by the reference character 42, and shown in further detail by FIG. 5. This suction hood superstructure comprises bonnet elements 44 and 46 arranged respectively above the cover plates 22 and 24 at either side of a tubular conduit member 48 extending through the space enclosed by the bonnet elements 44 and 46 in lengthwise relation to the lickerin 10. The bonnet elements 44 and 46 may alternatively be formed as a single continuous element, but in either event the respective extending bonnet edges 44' and 46' are arranged to assume a resting disposition at the top faces of the spacers 30 in adjacently spaced relation with respect to the cylinder cover plate 20 and the feed roll 12, respectively. The ends of the bonneted space are closed by end wall members 50 and 52 fitted at either side of the tubular conduit member 48 and jointly carrying an attaching flange 54 by which the superstructure 42 is secured in place on the spacers 30 as indicated at 56 in FIG. 1.

As seen in FIG. 5 at 58 and 58, the tubular conduit member 48 extends beyond the bonneted space at both ends so that a suction source may be connected thereto at either side of the carding machine. When a given conduit end extension 58 or 58 is selected for the suction connection, the other end is fitted with a closure cap (not shown) so that the connected suction is caused to draw from the bonneted space through lateral conduit apertures 60 and 60 (compare FIGS. 1 and 5) located at a substantially central position with respect to the length of the lickerin 10.

The result of the foregoing arrangement and disposition of the suction hood superstructure 42 is to provide means for inducing an air draft outwardly through the spacing between the overlapping edge portions of the concentric and eccentric cover plates 22 and 24 to obtain the previously mentioned air release directed reversely from the lickerin surface. FIG. 1 indicates the general path of the lickerin air currents 10 as this direction reversal takes place well ahead of the feed roll 12 under the influence of the outward draft induced through the spacing between the overlapped cover plates 22 and 24.

The described disposition of the superstructure 42 on the spacers 30 additionally results in leaving the bonnet enclosed spaced open sufficiently beneath the extending bonnet edges 44' and 46 to induce further air drafts respectively adjacent the outer face of the cylinder cover plate 20 and above the feed roll 12, as indicated in FIG. 1 at 20 and 12', so that a continual collecting action is applied quite effectively with respect to the ambient fiber fly that is regularly generated above the lickerin position by release of the cylinder air currents 18 above the cylinder cover plate 20, and that collects objectionably on the carding machine over a period of time unless dealt with as it is generated.

The provision for setting the eccentric cover plate 24 by means of the adjusting screws 38 makes it possible to vary the spacing above the terminal edge portion of the concentric cover plate 22 so as to modulate the reversely directed air withdrawal therethrough at the level needed for controlling the lickerin air currents at the operating speed involved, while maintaining a suitably balanced relation of the further air drafts 20 and 12.

FIG. 6 illustrates an elaborated embodiment of the invention in which provision is made for fiber and air control at the carding cylinder as well as the lickerin; the lickerin 10, feed roll 12, feed plate 14, and understructure 16 being shown in relation to the carding cylinder 18, with a first concentric shroud plate 62 disposed at the cylinder surface comparably to the conventional cylinder cover plate 20, and as a counterpart of the concentric lickerin cover plate 22. A second complementary shroud plate 64 is additionally disposed at the cylinder surface, as a counterpart of the eccentric lickerin cover plate 24, and is arranged to overlap and space the adjacent edge portions of these cylinder shroud plates 62 and 64 so that the cylinder air currents 18' are released reversely through the spacing between the overlapping shroud plate edge portions. In order to induce the reversely directed air release from the cylinder surface, an additional suction hood superstructure 66 is provided over the cylinder shroud plates 62 and 64 in all respects similar to the previously described suction hood 42 at the lickerin. The space needed for installing a fiber and air control means of the foregoing sort at the cylinder 18, beyond the lickerin 10, may be provided by shortening the reach of the carding flats 68 so that they operate about pulleys 70 at the usual grind stand location, rather than reaching farther down the cylinder surface toward the lickerin 10 as is normally the case.

The result of installing the described fiber and air control means at the cylinder in accordance with the present invention is to make possible a much improved regulation of fiber quality during carding; It has previously been noted that when used at the lickerin the present invention provides advantageously for withdrawing undesirable short fiber thereat, but as the returning untransferred fiber on the lickerin is only in the order of 10 percent of the feed, the short fiber removal at the lickerin can only be a relatively small portion of the total that should desirably be removed. By applying the same air control principle to the cylinder so as to operate on all of the fiber being carded, a total control of short fiber removal is possible to produce carded sliver having a quality very substantially improved in the direction of combing as compared with usual carding results.

The present invention, accordingly, not only provides for considerably improved air control over the arrangements disclosed for this purpose in our copending application Ser. No. 489,590, filed Sept. 23, 1965 now U.S. Pat. No. 3,357,062, but additionally makes possible a substantial improvement in carding quality through fiber control, and the invention has been described in detail above for purposes of illustration only and is not intended to be limited by this description or otherwise except as defined in the appended claims.

We claim:

1. In a carding machine, the combination with a carding cylinder, and a lickerin roll operating thereat to feed the cylinder, of a first arcuate cover plate shrouding said cylinder beyond said lickerin roll, a second arcuate cover plate shrouding the surface of said lickerin roll beyond said cylinder in converging and abutting relation to said first cover plate, a third arcuate cover plate additionally shrouding the surface of said lickerin roll in complementary relation with respect to said second cover plate, said second cover plate extending from said first cover plate concentrically over said lickerin roll in relatively close shrouding relation thereto said third complementary cover plate overlapping the adjacent edge portion of said second cover plate and extending therebeyond eccentrically over said lickerin roll so as to space the overlapping edge portions of said second and third cover plates, and means for inducing an air draft outwardly through the spacing between said overlapping edge portions.

2. In a carding machine, the combination with a carding cylinder, and a lickerin roll operating thereat to feed the cylinder from the delivery of a feed roll cooperating with a feed plate at said lickerin in approximate diametrically opposite relation to said cylinder, of a first arcuate cover plate shrouding said cylinder beyond said lickerin roll, second and third complementary arcuate cover plates shrouding the surface of said lickerin roll beyond said cylinder to said feed roll, said second cover plate extending from converging and abutting relation with said first cover plate concentrically over said lickerin roll in relatively close shrouding relation thereto in an extent terminating short of said feed roll, said third cover plate overlapping the adjacent edge portion of said second cover plate and extending therebeyond to said feed roll eccentrically over said lickerin roll so as to space the overlapping edge portion thereof with respect to the overlapped edge portion of said third cover plate, and means for inducing an air draft outwardly through the spacing between said edge portions.

3. In a carding machine, the combination defined by claim 2 and further characterized in that said third cover plate is pivotally mounted adjacent said feed roll, and in that means is provided for adjustably setting the overlapping edge portion thereof at a selected spacing with respect to the overlapped edge portion of said second cover plate.

4. In a carding machine, the combination defined by claim 2 and further characterized in that said draft inducing means comprises a suction hood superstructure disposed over said second and third cover plates to impose an exterior suction at the spacing between said overlapping cover plate edge portions.

5. In a carding machine, the combination defined by claim 4 and further characterized in that said suction hood superstructure comprises a bonnet mounted above said second and third cover plates and a tubular conduit member extending through said bonnet in lengthwise relation to said lickerin roll with lateral apertures formed therein at a substantially central position with respect to the length of said roll for imposing said external suction within said bonnet.

6. In a carding machine, the combination defined by claim and further characterized in that said bonnet encloses a space above said second and third cover plates that extends to each side of said tubular conduit member respectively toward said first cover plate and said feed roll, and in that said bonnet has respective extending edges arranged parallel and remotely with respect to said tubular conduit member and terminating short of the respectively adjacent structure to leave the bonnet enclosed space open sufficiently thereat to induce additional suction drafts respectively adjacent said first cover plate and said feed roll from said tubular conduit member.

7. The method of controlling the character of fiber going forward on a carding machine roll surface, which method comprises shrouding said roll surface relatively closely for an extent sufficient to direct air currents generated at said roll surface for seating fiber carried thereon in the clothing thereat, shrouding said roll surface further in the traveling direction thereof while providing for reversely directed air release through the shrouding immediately beyond said relative close shrouding and then withdrawing air through said shrouding from said roll surface in a direction reverse to the traveling direction thereof and thereby limiting entrained fiber removal from said roll surface predominantly to undesirable short fiber, while predominantly retaining usable long fiber on said roll surface.

8. The method defined in claim 7 and further characterized in that said reversely directed air withdrawal is modulated at a level sufficient for removing a selected portion of all undesirable short fiber from said roll surface.

9. In a carding machine, the combination with a fiber carrying roll surface thereof of a first means disposed for shrouding said roll surface relatively closely for an extent sufficient to direct air currents generated at said roll surface for seating fiber carried thereon in the clothing thereat, a complementary second shroud means disposed at said roll surface in following relation to said first means to overlap the downstream edge portion thereof in spaced relation thereto for releasing air from said roll surface between the overlapping portions of said first and second shroud means reversely with respect to the roll surface traveling direction thereof, and means for adjusting the position of said second shrouding means relative to said first shrouding means to modulate the reversely directed air release at a level sufficient for removing a selected proportion of all undesirable short fiber from said roll surface while predominantly retaining usable long fiber thereon.

10. In a carding machine, the combination with a fiber carrying roll surface thereof of first means concentrically disposed at said roll surface for shrouding the same relatively closely for an extent sufficient to direct air currents generated thereat for seating fiber carried thereon in the surface clothing, and a complementary second shroud means disposed atsaid roll surface in following relation to said first means to overlap the downstream edge portion thereof and space the adjacent edge portions of said first and second means, and means for inducing an air draft through the spacing between said overlapping edge portions reversely with respect to the traveling direction of said roll surface,

whereby fiber removed from said roll surface is limited predominantly to undesirable short fiber while usable long fiber is predominantly retained on said roll sur- 

1. In a carding machine, the combination with a carding cylinder, and a lickerin roll operating thereat to feed the cylinder, of a first arcuate cover plate shrouding said cylinder beyond said lickerin roll, a second arcuate cover plate shrouding the surface of said lickerin roll beyond said cylinder in converging and abutting relation to said first cover plate, a third arcuate cover plate additionally shrouding the surface of said lickerin roll in complementary relation with respect to said second cover plate, said second cover plate extending from said first cover plate concentrically over said lickerin roll in relatively close shrouding relation thereto, said third complementary cover plate overlapping the adjacent edge portion of said second cover plate and extending therebeyond eccentrically over said lickerin roll so as to space the overlapping edge portions of said second and third cover plates, and means for inducing an air draft outwardly through the spacing between said overlapping edge portions.
 2. In a carding machine, the combination with a carding cylinder, and a lickerin roll operating thereat to feed the cylinder from the delivery of a feed roll cooperating with a feed plate at said lickerin in approximate diametrically opposite relation to said cylinder, of a first arcuate cover plate shrouding said cylinder beyond said lickerin roll, second and third complementary arcuate cover plates shrouding the surface of said lickerin roll beyond said cylinder to said feed roll, said seconD cover plate extending from converging and abutting relation with said first cover plate concentrically over said lickerin roll in relatively close shrouding relation thereto in an extent terminating short of said feed roll, said third cover plate overlapping the adjacent edge portion of said second cover plate and extending therebeyond to said feed roll eccentrically over said lickerin roll so as to space the overlapping edge portion thereof with respect to the overlapped edge portion of said third cover plate, and means for inducing an air draft outwardly through the spacing between said edge portions.
 3. In a carding machine, the combination defined by claim 2 and further characterized in that said third cover plate is pivotally mounted adjacent said feed roll, and in that means is provided for adjustably setting the overlapping edge portion thereof at a selected spacing with respect to the overlapped edge portion of said second cover plate.
 4. In a carding machine, the combination defined by claim 2 and further characterized in that said draft inducing means comprises a suction hood superstructure disposed over said second and third cover plates to impose an exterior suction at the spacing between said overlapping cover plate edge portions.
 5. In a carding machine, the combination defined by claim 4 and further characterized in that said suction hood superstructure comprises a bonnet mounted above said second and third cover plates and a tubular conduit member extending through said bonnet in lengthwise relation to said lickerin roll with lateral apertures formed therein at a substantially central position with respect to the length of said roll for imposing said external suction within said bonnet.
 6. In a carding machine, the combination defined by claim 5 and further characterized in that said bonnet encloses a space above said second and third cover plates that extends to each side of said tubular conduit member respectively toward said first cover plate and said feed roll, and in that said bonnet has respective extending edges arranged parallel and remotely with respect to said tubular conduit member and terminating short of the respectively adjacent structure to leave the bonnet enclosed space open sufficiently thereat to induce additional suction drafts respectively adjacent said first cover plate and said feed roll from said tubular conduit member.
 7. The method of controlling the character of fiber going forward on a carding machine roll surface, which method comprises shrouding said roll surface relatively closely for an extent sufficient to direct air currents generated at said roll surface for seating fiber carried thereon in the clothing thereat, shrouding said roll surface further in the traveling direction thereof while providing for reversely directed air release through the shrouding immediately beyond said relative close shrouding and then withdrawing air through said shrouding from said roll surface in a direction reverse to the traveling direction thereof and thereby limiting entrained fiber removal from said roll surface predominantly to undesirable short fiber, while predominantly retaining usable long fiber on said roll surface.
 8. The method defined in claim 7 and further characterized in that said reversely directed air withdrawal is modulated at a level sufficient for removing a selected portion of all undesirable short fiber from said roll surface.
 9. In a carding machine, the combination with a fiber carrying roll surface thereof of a first means disposed for shrouding said roll surface relatively closely for an extent sufficient to direct air currents generated at said roll surface for seating fiber carried thereon in the clothing thereat, a complementary second shroud means disposed at said roll surface in following relation to said first means to overlap the downstream edge portion thereof in spaced relation thereto for releasing air from said roll surface between the overlapping portions of said first and second shrouD means reversely with respect to the roll surface traveling direction thereof, and means for adjusting the position of said second shrouding means relative to said first shrouding means to modulate the reversely directed air release at a level sufficient for removing a selected proportion of all undesirable short fiber from said roll surface while predominantly retaining usable long fiber thereon.
 10. In a carding machine, the combination with a fiber carrying roll surface thereof of first means con-centrically disposed at said roll surface for shrouding the same relatively closely for an extent sufficient to direct air currents generated thereat for seating fiber carried thereon in the surface clothing, and a complementary second shroud means disposed at said roll surface in following relation to said first means to overlap the downstream edge portion thereof and space the adjacent edge portions of said first and second means, and means for inducing an air draft through the spacing between said overlapping edge portions reversely with respect to the traveling direction of said roll surface, whereby fiber removed from said roll surface is limited predominantly to undesirable short fiber while usable long fiber is predominantly retained on said roll surface. 